System and method for exposing an object to an electrical discharge

ABSTRACT

A conveyor system for exposing an object to an electrical discharge to increase the surface tension of a surface of the object comprises a guide, a first conveyor, an electrode, and a second conveyor. The first conveyor is configured to convey the object toward the guide. The electrode is configured to provide an electrical discharge. The guide and the second conveyor are configured to rotate the object for exposure to the electrical discharge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Application No.10/284,812 filed Oct. 31, 2002, which claims the benefit of U.S.Provisional Application No. 60/422,294, filed Oct. 30, 2002, both ofwhich are incorporated by reference herein in their entirety.

BACKGROUND

In the field of exposing an object to an electrical discharge, one knownmethod is corona treatment. Corona treatment is the exposure of anobject to a corona discharge, which is generated by exposing atmosphericair to different voltage potentials. A corona is the faint glowenveloping from an electrode in a corona discharge, often accompanied bystreamers directed toward a second electrode. When a plastic substanceis placed under the corona discharge, the electrons generated in thedischarge impact on a surface of the substance to be treated withsufficient energy to break the molecular bonds on the treatment surface.Oxidation of the treatment surface increases the surface energy,allowing for better wetting by liquids and promoting adhesion. Theoxidation results in an improved surface tension, which advantageouslyprovides for improved bonding of liquids, adhesives, and inks to plasticsurfaces and other surfaces.

One use for corona treatment is in treating the surfaces of plasticcontainers which contain household (and other) products, such asshampoo, cleaner, oil, paint, etc. One challenge in treating thesecontainers is that the containers come in various shapes and sizes.Therefore, it would be advantageous to have a system for exposing a widevariety of extrusion or injection blow molded containers to anelectrical discharge without requiring adjustment of the treatmentsystem.

In one prior method of treating polyolefin objects, a conveyor beltprovides an object to an electrical discharge apparatus for treatment.However, this system requires an alignment plate and an adjustableguiding arm. This system has the disadvantage of requiring operatoradjustment to accommodate different treatment processes.

Accordingly, what is needed is an improved system and method forexposing an object to an electrical discharge. Further, there is a needfor such a system which does not require operator adjustments toaccommodate various sizes and shapes of objects to be treated. Furtherstill, there is a need for a system which has a conveyor mechanismwhich, when worn, can be more quickly and inexpensively replaced.Further still, what is needed is a system having a conveyor mechanismthat does not require belt tensioning or belt alignment systems. Furtherstill, what is needed is an improved guide having less rapid wear of theguide (due to the corona discharge between the guide and the electrode)and more optimal treatment of the object to be treated. Further still,what is needed is an improved wire electrode for optimal treatment ofthe object to be treated. Further still, what is needed is an improvedsystem and method of providing the object at a predetermined distancefrom the electrode with better reliability than prior systems.

The teachings hereinbelow extend to those embodiments which fall withinthe scope of the appended claims, regardless of whether they accomplishone or more of the above-mentioned needs.

SUMMARY

According to one exemplary embodiment, a conveyor system for exposing anobject to an electrical discharge to increase the surface tension of asurface of the object comprises a guide, a first conveyor, an electrode,and a second conveyor. The first conveyor is configured to convey theobject toward the guide. The electrode is configured to provide anelectrical discharge. The guide and the second conveyor are configuredto rotate the object for exposure to the electrical discharge.

According to another exemplary embodiment, a conveyor system forexposing an object to an electrical discharge comprises an electrode, aconveyor, and a fixed, non-adjustable guide. The electrode is configuredto provide an electrical discharge to the object to change the surfacetension of a surface of the object. The fixed, non-adjustable guide isdisposed between the electrode and the object. The conveyor isconfigured to convey the object against the guide member.

According to yet another exemplary embodiment, a system for exposing anobject to an electrical discharge comprises an electrode, a firstconveyor, and a second conveyor. The electrode is configured to providean electrical discharge. The first conveyor comprises a first beltmoving in a first direction configured to move the object toward theelectrode. The second conveyor comprises a second belt moving in asecond direction not parallel to the first direction. The secondconveyor is configured to rotate and move the object for exposure to theelectrical discharge. The surface tension of a surface of the object ischanged.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, wherein like reference numerals refer to like parts andwherein:

FIG. 1 is a front view of a system for exposing an object to anelectrical discharge, according to an exemplary embodiment;

FIG. 2 is a right side view of the system of FIG. 1, according to anexemplary embodiment;

FIG. 3 is a cutaway view taken along line 3-3 in FIG. 1, according to anexemplary embodiment;

FIG. 4 is a cutaway view taken along line 4-4 of FIG. 1, according to anexemplary embodiment;

FIG. 5 is a front view of a guide, according to an exemplary embodiment;and

FIG. 6 is a cutaway view taken along line 6-6 in FIG. 1, according to anexemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring to FIG. 1, a treatment system 10 is shown. Treatment system 10is a system for exposing an object to an electrical discharge. In thisexemplary embodiment, the electrical discharge changes the surfacetension of a surface of the object by oxidizing the surface to make thesurface receptive to inks, adhesives, etc.

The object can have a treatment surface comprising plastic, such as apolyolefin, polypropylene, polyethylene, PET, etc., a metal, nylon,vinyl, foils, paper, paperboard stock and/or other materials. The objectcan have one or more of curved or flat surfaces, but preferably have acurved surface which is circular or oval in cross-section. Treatmentsystem 10 can treat cylindrical and rounded oval containers in the rangeof ¼ oz. to 1 gallon (8 oz. to 3.87 Liters), or more.

The objects to be treated can be cylindrical, having an outside diameterof 0.25 to 8 inches (6.3 mm to 200 mm) and a height of 0.5 inch or more(12.5 mm), or rounded oval containers having a width of 0.5 inch to 6inches (12.5 mm to 150 mm), a depth of 0.5 inch to 6 inches (12.5 mm to150 mm), and a height of 0.5 inch to 16 inches (12.5 mm to 406 mm).Alternative sizes and shapes are contemplated. For example, analternative embodiment of system 10 can be configured to treat objectshaving a diameter of twelve inches (300 mm), two feet (600 mm), or moreand a height of six inches (150 mm) or more.

Treatment system 10 is designed for convenient installation into moldingand/or printing lines and comprises a loading platform 20 and anunloading platform 22. Loading platform 20 is configured to receiveobjects to be treated and unloading platform 22 is configured to providetreated objects to subsequent manufacturing steps. Treatment system 10can also be used as a stand-alone workstation.

Referring again to FIG. 1, a plurality of subsystems of treatment system10 are illustrated in block diagram form. A power supply 12 isconfigured to receive an input voltage and to provide power to one ormore high voltage transformers 17. An operator interface 14 is coupledto a control system 15, which is coupled to at least one of power supply12 and conveyor system 16 to allow an operator or user to control thestarting and stopping of conveyor system 16 and to control otherfunctions of treatment system 10. Operator interface can includebuttons, switches, etc. and also output devices, such as a display,lights, a buzzer, etc.

Power supply 12 is configured to provide power to transformers 17.Transformers 17 provide high voltage power to electrodes 18, which canbe between 0 and 50 mA of 6-75 kHz electricity at between 10 and 100 kV.Electrodes 18 (wire electrode 32 and counter electrode 34, as shown inFIG. 3) are disposed in the vicinity of the objects to be treated togenerate a corona or other electrical discharge to treat the surface ofthe objects. In this embodiment, transformers 17 comprise a firsttransformer configured to provide high voltage power to one electrodeand a second transformer configured to provide high voltage power to asecond electrode. The two transformers provide high voltage power torespective electrodes out of phase, and the voltages can be the same ordifferent. Alternatively, one transformer can provide power to oneelectrode 18, while the other electrode is on ground potential.Electrodes 18, high voltage transformers 17 and power supply 12 areconfigured to provide treatment of up to 70 milliNewtons/Meter (mN/M ordyne/cm), depending on the application. Control system 15 (e.g.,comprising one or more digital and/or analog control components, suchas, a microprocessor, a microcontroller, an application-specificintegrated circuit, etc.) is configured to control conveyor system 16with a speed of 32 feet (10.7 m) per minute or less. Alternatively,conveyor system 16 can be operated at speeds greater than 32 feet perminute.

Referring now to FIG. 2, a right side view of treatment system 10 isshown, illustrating an intake aperture 24 configured to receive theobjects to be treated. An ozone exhaust and filter connection and/orsystem 26 is provided to reduce the ozone level in and around treatmentsystem 10.

Referring now to FIG. 3, treatment system 10 is shown in a cutaway view.In this exemplary embodiment, treatment system 10 comprises a conveyorsystem 28 comprising a conveyor 30, first and second electrodes 32, 34(e.g., both electrodes having the same or similar power level 180degrees out of phase), and a guide 36. Conveyor 30 moves or conveysobjects 38 through treatment system 10 and can comprise any of aplurality of conveying or moving mechanisms, such as conveyor belts,actuators, motors, robotic arms, pulleys, air flow or suction devices,rollers, etc. In this exemplary embodiment, conveyor 30 comprises afirst conveyor 40 configured to convey objects 38 toward guide 36 andelectrode 32. Conveyor 30 further comprises one or more second conveyors42, 44, and 46 configured to move and rotate objects 38. Conveyor 30further comprises a third conveyor 48 configured to convey objects alongunloading platform 22 away from electrode 32. Each of conveyors 40-48comprises a corresponding motor, which can be a DC motor, servo motor,drive motor, or other motor, and a conveyor belt or belts. It isunderstood that different embodiments of conveyor 30 can have one, two,or three conveyors (or more) performing various moving or rotatingfunctions, and that conveyors can include belts or alternative conveyingmechanisms, such as, a robotic arm, roller, etc.

According to one advantageous aspect of this embodiment, the conveyorbelt of one or more of conveyors 40-48 comprises a plurality of flexibleor bendable or stretchable belts. Each belt is flexible and can compriseurethane in a toroid or “O”-ring shape having a cross-sectional diameteror thickness of approximately one-eighth of an inch, or less than oneinch. In this embodiment, each of conveyors 40-48 comprises at leastthree “O”-ring shaped belts, each belt having a thickness ofapproximately one-quarter of an inch. Alternative materials can be used.The motor or motors (only one motor drives all of conveyors 40-48 inthis exemplary embodiment) of each of conveyors 40-48 are driven undercontrol of control system 15 and operator interface 14 (FIG. 1) torotate the plurality of belts to impart movement on objects 38 throughtreatment system 10.

In one example, a motor 52 drives a pulley 54 to rotate belts 50. Pulley54 has an open end 55 to allow for easy changing of belts. Furthermore,the stretchability of the belts also provides for easy changing of thebelts. Furthermore, belt tensioning and alignment systems are notrequired in the embodiment shown. Corona treatment can discolor, damage,or wear away at the belts over a long period of time and, therefore, itis advantageous to have belts which are easily replaceable. Inalternative embodiments, belts 50 can be a conventional one-piecesheet-type belt.

First conveyor 40 is configured to receive objects 38 and convey theobjects toward electrode 32 and guide 36. Second conveyors 42-46 areconfigured to rotate objects 38 for exposure to electrical dischargefrom electrode 32. In this embodiment, second conveyors 42-46 have beltswhich are disposed and/or which move along an axis non-parallel to beltsof first conveyor 40 and/or third conveyor 48. Second conveyors 42-46have belts which are disposed or provided at an angle 53 ofapproximately 60 degrees (which may be greater or less than 60 degrees,such as, any angle between 5 degrees and 85 degrees) relative to thebelts of first conveyor 40. The belts of second conveyors 42-46 are alsoangled relative to the direction of travel of objects 38, which travelalong the longitudinal axis of objects 38 in this exemplary embodiment.Second conveyors 42-46 may number one, two, or more, but preferablyinclude three separate conveyor mechanisms. Each mechanism may have amotor and a plurality of belts, or all mechanisms may be driven by asingle motor. Second conveyors 42-46 are configured to rotate objects 38and to push objects 38 against guide 36 while conveying objects 38 alongthe same direction of travel as conveyed by first conveyor 40.

Referring to FIG. 4, it is shown that, according to one exemplaryembodiment, second conveyors 42-46 are inclined at an angle 56, whichcan be 15 degrees, or can be greater or less than 15 degrees, relativeto a plane perpendicular with the ground beneath system 10 or a bottomsurface of system 10. In this embodiment gravity provides furtherpushing of objects 38 against guide 36.

Referring again to FIG. 3, electrode 32 comprises a wire electrode 58 inthis embodiment. Advantageously, wire electrode 58 forms a loop or arectangle with a wire electrode having a cross-sectional diameter ofless than 0.25 inches. An electrode having a cross-sectional diameter ofless than 0.25 inches is advantageous for treating empty containers withan optimal electrical discharge. Electrode 32 is further coupled toinsulators/isolators 60 (FIG. 4) and to transformers 17 (FIG. 1). Inthis exemplary embodiment, wire electrode 58 comprises stainless steeland is manufactured by a cold draw method. The cold draw methodcomprises providing a stainless steel wire of a predetermined length andcross-sectional diameter and drawing the wire, i.e., providing a pullingforce on ends of the wire. The pulled or drawn wire has a greater lengthand smaller, controlled cross-section diameter and surface finish thanbefore the pulling operation. Preferably, the pulling is done withoutthe use of applied heat. Cold drawn stainless steel wire can be two toten times the hardness of other stainless steel wires, which makes itmore durable and more resistant to scratches. A scratch or imperfectionin the wire can result in a high volume of streamers during coronatreating which can result in uneven treatment of the object to betreated. The smaller the diameter of wire electrode 58, the easier it isfor electrical discharge to release from the electrode with a lowerdriving voltage.

Another advantageous feature of wire electrode 58 is that it comprisescorners 100, 102 which are curved with a large radius, preferably morethan 0.25 inches or between 0.25 inches and 3 inches. A sharp edge atcorners 100, 102 can result in an intense discharge of electricity,which can result in uneven treatment and can degrade or even melt thedielectric material in electrode 34.

In this exemplary embodiment, wire electrode 58 has a rectangular shapecomprising a treatment side 61 having a length of approximately 17inches (though it may be greater or less than 17 inches in alternativeembodiments). The greater the length of treatment side 61, the fasterthat objects 38 can be moved and rotated across wire electrode 58 byconveyor 30.

A second electrode 34 is disposed a predetermined distance 62 (FIG. 4)from first electrode 32. Referring to FIG. 6, second electrode 34 isshown in greater detail. Second electrode 34 comprises a dielectricmaterial 80 defining a U-shaped recess 82. A metal counter electrode 84is disposed in U-shaped recess 82 and held in a fixed position in partby a casing 86. Dielectric material 80 can comprise polyethylene,silicone, ceramic, glass, Teflon, or other dielectric materials. Recess82 can be bored into dielectric material 80 and can take any of avariety of shapes. Electrode 84, which can comprise aluminum, is coupledto transformer 17 and is configured to receive a high voltagealternating power from transformer 17 for producing an electricaldischarge between electrodes 32 and 34. Casing 86 can be silicone oranother material configured to encase electrode 84. Electrodes 32 and 34are fixed to a base or housing 90 of treatment system 10, which can be ametal rail, frame, or other base or housing. Advantageously, in thisembodiment, both first electrode 32 and second electrode 34 are fixedand non-user-adjustable to provide for improved convenience for the userand because conveyor 30 does not require adjustment to treat containershaving different sizes and shapes.

Referring again to FIG. 3, conveyor 30 further comprises a guide 36which can be any type of material, such as metal, plastic, etc. Secondconveyor 42-46 is configured to rotate objects 38 against guide 36 toprovide exposure of surfaces (preferably 360 degrees of surfaces) ofobjects 38 to electrical discharge from electrode 32. Further, guide 36and second conveyor 42-46 maintain objects 38 at the same longitudinalalignment of objects 38 as on first conveyor 40.

While guide 36 may take many embodiments, in this embodiment guide 36 isa thin-walled guide mask which is fixed and not user adjustable. Guide36 is a nonconductive plastic sheet (e.g., Mylar, PET, etc.) or othermaterials having a high tensile strength, dimensional stability, highelectrical insulating properties, and/or resistant to oil, water andozone. Guide 36 provides a spring tensioning device 68 and 70 configuredprovide tension to guide 36 by pulling guide 36 firmly into a fixed,non-user-adjustable position for improved guiding of objects 38. Mask 36is preferably 10 mills thick and two inches high, but can be greater orless than these dimensions. Preferably, guide 36 has a length thatexceeds the length of treatment side 61 of electrode 32. As illustratedin FIG. 5, mask 36 comprises an aperture 72 or electrode cut-out havinga length of approximately the length of treatment side 61 of electrode32 and a narrow width. Aperture or slot 72 provides an opening forelectrical discharge to travel from electrode 32 to objects 38. Due tothe thin wall of the mask, the mask has a minimum mass, and thedischarge will release through aperture 72 onto objects 38. A minimalamount of electrical discharge will occur between electrode 32 and mask36, reducing the wear of guide mask 36 and loss of electrical dischargetreatment.

Referring again to FIG. 3, third conveyor 48 is disposed parallel to theground, as is first conveyor 40 in this exemplary embodiment. Thirdconveyor 48 is configured to receive objects 38 from second conveyor42-46 and to convey objects 38 away from electrode 32. In an alternateembodiment, third conveyor 48 is not part of system 10, and objects 38are moved by second conveyors 42-46 directly to a collecting bin outsideof system 10, or to a conveyor of another processing system.

In operation, objects 38 are provided to first conveyor 40 at loadingplatform 20 and are conveyed by first conveyor 40 to second conveyor42-46. The functions of first conveyor 40 and second conveyor 42-46 canbe combined into a single conveyor. Notably, objects 38 maintain thesame direction of travel and same orientation (along the longitudinalaxis of objects 38) as objects 38 move from first conveyor 40 to secondconveyor 42-46.

Second conveyor 42-46 and guide 36 are configured to rotate objects 38axially or around a longitudinal axis 74 of objects 38 for exposure toelectrical discharge from electrode 32 through aperture 72 (FIG. 5) ofguide 36. The angle of incline 56 (FIG. 4) of second conveyor 42-46provides improved contact between second conveyor 42-46 and guide 36.Second conveyor 42-46 is configured to convey objects 38 betweenelectrode 32 and second electrode 34. The electrical discharge fromelectrodes 32 and/or 34 is sufficient to oxidize a surface, andpreferably surfaces on all sides of object 38 to make the surfacesreceptive to inks, adhesives, liquids, etc. Second conveyor 42-46 andguide 36 are configured to rotate objects 38 at least one 360°revolution (which may be more or less than a full 360° revolution inalternative embodiments) and to move objects 38 to third conveyor 48 forremoval from treatment system 10. Thus, conveyor 30 has a loadingportion at first conveyor 40 configured to receive the object and atreatment portion at a portion of second conveyor 42-46 near electrode32, wherein the conveyor is configured to maintain objects 38 in thesame longitudinal alignment in both the loading portion and thetreatment portion. Further, second conveyor 42-46 and guide 36 cooperateto maintain a treatment surface of object 38 at a pre-determineddistance from electrode 32 to insure a uniform treatment. Thispredetermined distance is not user-adjustable in this embodiment.

First conveyor 40 and second conveyor 42-46 can be coplanar, oralternatively may be non-coplanar, such as, where second conveyor 42-46is inclined. In an embodiment were second conveyor 42-46 is inclined andnon-parallel with first conveyor 40, optimal pressure is provided topush object 38 against electrode 32 to provide consistent treatment byelectrical discharge.

In this embodiment, second conveyors 42-46 are coplanar with each other,but in alternative embodiments, they may be non-coplanar and one or moreof second conveyors 42-46 may drive belts parallel with conveyor 40and/or conveyor 48.

Guide 36 is a single guide in this embodiment, but may alternatively bemultiple guides and may be provided at different locations.

While the exemplary embodiments illustrated in the FIGS. and describedabove are presently preferred, it should be understood that theseembodiments are offered by way of example only. Accordingly, the presentinvention is not limited to a particular embodiment, but extends tovarious modifications that nevertheless fall within the scope of theappended claims.

1. A conveyor system for exposing an object to an electrical dischargeto increase the surface tension of a surface of the object, comprising:a guide; a first conveyer configured to convey the object toward theguide; an electrode configured to provide an electrical discharge; and asecond conveyor, wherein the guide and the second conveyor areconfigured to rotate the object for exposure to the electricaldischarge.
 2. The conveyor system of claim 1, wherein the objectmaintains the same longitudinal alignment on the first conveyor and thesecond conveyor.
 3. The conveyor system of claim 1, wherein the firstconveyor has a belt which is nonparallel to a belt of the secondconveyor.
 4. The conveyor system of claim 1, wherein the second conveyorhas an inclined belt configured to push the object against the guide. 5.The conveyor system of claim 1, wherein the second conveyor comprises aplurality of flexible belts.
 6. The conveyor system of claim 5, whereinthe plurality of flexible belts have a cross-sectional diameter of lessthan approximately one inch.
 7. The conveyor system of claim 1, whereinthe first conveyor is configured to convey the object along a directionof travel and the second conveyor is configured to convey the objectalong the same direction of travel and to push the object against theguide.
 8. The conveyor system of claim 1, further comprising a thirdconveyor configured to receive the object from the second conveyor andto convey the object away from the electrode.
 9. The conveyor system ofclaim 1, further comprising a second electrode, wherein the secondconveyor is configured to convey the object between the electrode andthe second electrode.
 10. The conveyor system of claim 1, wherein theelectrode is in a fixed position relative to the guide.
 11. The conveyorsystem of claim 1, wherein the electrical discharge is configured tooxidize a surface of the object to make the surface receptive to atleast one of inks and adhesives.
 12. A conveyor system for exposing anobject to an electrical discharge, comprising: an electrode configuredto provide an electrical discharge to the object to change the surfacetension of a surface of the object; a conveyor; and a fixed,non-adjustable guide disposed between the electrode and the object,wherein the conveyor is configured to convey the object against theguide member.
 13. The conveyor system of claim 12, further comprising asecond electrode, wherein the conveyor is configured to convey theobject between the electrode and the second electrode.
 14. The conveyorsystem of claim 12, wherein the conveyor has a loading portionconfigured to receive the object and a treatment portion near theelectrode, wherein the conveyor is configured to maintain the object inthe same longitudinal alignment in both the loading portion and thetreatment portion.
 15. The conveyor system of claim 12, wherein theconveyor comprises a plurality of flexible belts.
 16. The conveyorsystem of claim 15, wherein the plurality of flexible belts have across-sectional diameter of less than approximately one inch.
 17. Asystem for exposing an object to an electrical discharge, comprising: anelectrode configured to provide an electrical discharge; a firstconveyor comprising a first belt moving in a first direction configuredto move the object toward the electrode; and a second conveyorcomprising a second belt moving in a second direction not parallel tothe first direction, wherein the second conveyor is configured to rotatethe object for exposure to the electrical discharge, whereby the surfacetension of a surface of the object is changed.
 18. The system of claim17, further comprising a guide configured to position the object at apredetermined distance from the electrode, wherein the predetermineddistance is not user-adjustable.
 19. The system of claim 18, wherein thesecond belt is inclined to push the object against the guide.
 20. Thesystem of claim 17, wherein the first conveyor and second conveyor haveconveying surfaces which are coplanar.